Mitochondrial encephalomyopathy with lactic acidosis and strokelike episodes (MELAS): a mitochondrial disorder presents as fibromyalgia.

This case report describes a patient who presented with symptoms and signs of longstanding fibromyalgia. Routine laboratory tests revealed an elevated anion gap. Evaluation of the elevated anion gap demonstrated elevated lactate and pyruvate levels and a lactate-to-pyruvate ratio greater than 20:1. A muscle biopsy was performed, exhibiting red ragged fibers, pathognomonic for a mitochondrial disorder. The patient was diagnosed with mitochondrial encephalomyopathy with lactic acidosis and strokelike episodes (MELAS). This is the first report describing fibromyalgia as the initial presentation of MELAS. This article outlines the diagnostic process that can assist the physician in distinguishing mitochondrial disorders from other muscular diseases, particularly fibromyalgia.